Queries a device driver about its checkpoint capabilities.
#include <sys/ioctl.h>int ioctl ( FileDescriptor, WPAR_CKPT_QUERY, Arg )
int FileDescriptor;
wpar_ckpt_resp_t * Arg;
| Item | Description |
|---|---|
| FileDescriptor | Open file descriptor that refers to the device being queried for the checkpoint capability. |
| WPAR_CKPT_QUERY | The command that requests information on the device checkpoint capability. |
| Arg | Pointer to a wpar_ckpt_resp_t structure which will contain a device driver response on the checkpoint capability upon a successful return from the ioctl call. |
The WPAR_CKPT_QUERY operation allows a caller to ask a device driver connected to the ioctl input file descriptor if it supports checkpoint and restart operations. If a device driver supports checkpoint and restart operations, the returned answer can describe what operations are required to accomplish a checkpoint and restart.
If the device is not checkpoint and restart capable, checkpoint-aware devices fail this ioctl request with the ENOSYS error. Non-checkpoint-aware devices fail this ioctl request as an unknown ioctl. If the device is checkpoint and restart capable, checkpoint-aware devices return success.
The arg parameter to a WPAR_CKPT_QUERY ioctl request allows the caller to receive specific information regarding how the device supports checkpoint and restart if it is capable. The caller of a WPAR_CKPT_QUERY ioctl request must supply a pointer to a structure of the wpar_ckpt_resp_t type in the arg parameter.
The wpar_ckpt_resp_t structure is supplied as the input to the WPAR_CKPT_QUERY ioctl request.
#define WPAR_CKPT_OP_MAX 5
typedef struct wpar_ckpt_resp_t {
int opcnt;
wpar_ckpt_op_top [WPAR_CKPT_OP_MAX];
}wpar_ckpt_resp_t;
The fields of the wpar_ckpt_resp_t structure are as follows:
| Item | Description |
|---|---|
| opcnt | Returned from an WPAR_CKPT_QUERY ioctl request as the number of the wpar_ckpt_op_t sub-structures that contain return information. |
| wpar_ckpt_op_top | A sub-structure that contains specific information on operation types that must occur on a device for it to save or restore its state correctly. |
The wpar_ckpt_op_t structure is a sub-structure of the wpar_ckpt_resp_t structure.
typedef struct wpar_ckpt_op_t {
int op;
int opt; /*extended options of openx*/
}wpar_ckpt_op_t;
The fields of the wpar_ckpt_op_t structure are as follows:
| Item | Description |
|---|---|
| op | Returned from a WPAR_CKPT_QUERY ioctl request. Defined as a set of one or more operations that must be performed to successfully checkpoint and restart the device. |
| opt | Options to supply to the openx function if the device is to be re-opened on the arrival server through the openx function. |
| Item | Description |
|---|---|
| WPAR_CKPT_OP_NULL | Device requires no special handling for checkpoint and restart operations. |
| WPAR_CKPT_OP_REOPEN | Device needs to be re-opened through the open function with the access modes applicable at checkpoint time. |
| WPAR_CKPT_OP_OPENX | Device needs to be re-opened with the openx function. The opt field denotes the desired extension argument to the openx function. |
Upon successful completion, this operation returns a value of 0. Otherwise, it returns a value of -1 and the errno global variable is set to one of the following values:
| Item | Description |
|---|---|
| ENOSYS | Device cannot participate in checkpoint and restart operations. |
| EINVAL | Device does not accept the WPAR_CKPT_QUERY operation. |